Sweep away soot
Cutting soot emissions from car exhausts, factories and open fires is probably the fastest way to tackle global warming, and there are calls for a treaty to achieve this. Scientists say the pollutant is the second biggest culprit in climate change after carbon dioxide. Black carbon, which gives soot its colour, has two main effects. It heats the atmosphere by absorbing radiation from the sun and releasing it into the air. And it darkens snow and ice when it falls on them, causing them to reflect less sunlight, heat up and melt – in turn exposing land or water, which also warms rapidly. Reducing emissions is fairly easy, using tried and tested technology. And it has a rapid effect as soot stays only days or weeks in the atmosphere, compared with centuries for carbon dioxide.